After working as a Title Examiner and as a Landman here in Texas for the last 12 years, Neil is correct as to there being no requirement of the time frame for searches here in Texas.  Most underwriters usually go back at least 40 years, sometimes 25 years depending on the circumstances.  Usually where the search involves recorded subdivisions, they usually start at the creation of the subdivision.  But again it is dependent on what the underwriters require.